diff --git a/src/librustc_back/target/aarch64_apple_ios.rs b/src/librustc_back/target/aarch64_apple_ios.rs
index 481338d1cee56..6530ccb0630db 100644
--- a/src/librustc_back/target/aarch64_apple_ios.rs
+++ b/src/librustc_back/target/aarch64_apple_ios.rs
@@ -8,11 +8,12 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use target::{Target, TargetOptions};
+use target::{Target, TargetOptions, TargetResult};
 use super::apple_ios_base::{opts, Arch};
 
-pub fn target() -> Target {
-    Target {
+pub fn target() -> TargetResult {
+    let base = try!(opts(Arch::Arm64));
+    Ok(Target {
         llvm_target: "arm64-apple-ios".to_string(),
         target_endian: "little".to_string(),
         target_pointer_width: "64".to_string(),
@@ -25,7 +26,7 @@ pub fn target() -> Target {
             features: "+neon,+fp-armv8,+cyclone".to_string(),
             eliminate_frame_pointer: false,
             max_atomic_width: 128,
-            .. opts(Arch::Arm64)
+            .. base
         },
-    }
+    })
 }
diff --git a/src/librustc_back/target/aarch64_linux_android.rs b/src/librustc_back/target/aarch64_linux_android.rs
index 81be546e0c89d..307823137a710 100644
--- a/src/librustc_back/target/aarch64_linux_android.rs
+++ b/src/librustc_back/target/aarch64_linux_android.rs
@@ -8,15 +8,15 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use target::Target;
+use target::{Target, TargetResult};
 
-pub fn target() -> Target {
+pub fn target() -> TargetResult {
     let mut base = super::android_base::opts();
     base.max_atomic_width = 128;
     // As documented in http://developer.android.com/ndk/guides/cpu-features.html
     // the neon (ASIMD) and FP must exist on all android aarch64 targets.
     base.features = "+neon,+fp-armv8".to_string();
-    Target {
+    Ok(Target {
         llvm_target: "aarch64-linux-android".to_string(),
         target_endian: "little".to_string(),
         target_pointer_width: "64".to_string(),
@@ -26,5 +26,5 @@ pub fn target() -> Target {
         target_env: "".to_string(),
         target_vendor: "unknown".to_string(),
         options: base,
-    }
+    })
 }
diff --git a/src/librustc_back/target/aarch64_unknown_linux_gnu.rs b/src/librustc_back/target/aarch64_unknown_linux_gnu.rs
index aec1bae60c812..14d0c8bedec1c 100644
--- a/src/librustc_back/target/aarch64_unknown_linux_gnu.rs
+++ b/src/librustc_back/target/aarch64_unknown_linux_gnu.rs
@@ -8,12 +8,12 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use target::Target;
+use target::{Target, TargetResult};
 
-pub fn target() -> Target {
+pub fn target() -> TargetResult {
     let mut base = super::linux_base::opts();
     base.max_atomic_width = 128;
-    Target {
+    Ok(Target {
         llvm_target: "aarch64-unknown-linux-gnu".to_string(),
         target_endian: "little".to_string(),
         target_pointer_width: "64".to_string(),
@@ -23,5 +23,5 @@ pub fn target() -> Target {
         target_os: "linux".to_string(),
         target_vendor: "unknown".to_string(),
         options: base,
-    }
+    })
 }
diff --git a/src/librustc_back/target/apple_ios_base.rs b/src/librustc_back/target/apple_ios_base.rs
index d182fd9605640..8bd9feabdbebe 100644
--- a/src/librustc_back/target/apple_ios_base.rs
+++ b/src/librustc_back/target/apple_ios_base.rs
@@ -36,7 +36,7 @@ impl Arch {
     }
 }
 
-pub fn get_sdk_root(sdk_name: &str) -> String {
+pub fn get_sdk_root(sdk_name: &str) -> Result<String, String> {
     let res = Command::new("xcrun")
                       .arg("--show-sdk-path")
                       .arg("-sdk")
@@ -55,12 +55,12 @@ pub fn get_sdk_root(sdk_name: &str) -> String {
                       });
 
     match res {
-        Ok(output) => output.trim().to_string(),
-        Err(e) => panic!("failed to get {} SDK path: {}", sdk_name, e)
+        Ok(output) => Ok(output.trim().to_string()),
+        Err(e) => Err(format!("failed to get {} SDK path: {}", sdk_name, e))
     }
 }
 
-fn pre_link_args(arch: Arch) -> Vec<String> {
+fn build_pre_link_args(arch: Arch) -> Result<Vec<String>, String> {
     let sdk_name = match arch {
         Armv7 | Armv7s | Arm64 => "iphoneos",
         I386 | X86_64 => "iphonesimulator"
@@ -68,8 +68,10 @@ fn pre_link_args(arch: Arch) -> Vec<String> {
 
     let arch_name = arch.to_string();
 
-    vec!["-arch".to_string(), arch_name.to_string(),
-         "-Wl,-syslibroot".to_string(), get_sdk_root(sdk_name)]
+    let sdk_root = try!(get_sdk_root(sdk_name));
+
+    Ok(vec!["-arch".to_string(), arch_name.to_string(),
+         "-Wl,-syslibroot".to_string(), sdk_root])
 }
 
 fn target_cpu(arch: Arch) -> String {
@@ -82,13 +84,14 @@ fn target_cpu(arch: Arch) -> String {
     }.to_string()
 }
 
-pub fn opts(arch: Arch) -> TargetOptions {
-    TargetOptions {
+pub fn opts(arch: Arch) -> Result<TargetOptions, String> {
+    let pre_link_args = try!(build_pre_link_args(arch));
+    Ok(TargetOptions {
         cpu: target_cpu(arch),
         dynamic_linking: false,
         executables: true,
-        pre_link_args: pre_link_args(arch),
+        pre_link_args: pre_link_args,
         has_elf_tls: false,
         .. super::apple_base::opts()
-    }
+    })
 }
diff --git a/src/librustc_back/target/arm_linux_androideabi.rs b/src/librustc_back/target/arm_linux_androideabi.rs
index e1b170422c60d..f3a18b13c6783 100644
--- a/src/librustc_back/target/arm_linux_androideabi.rs
+++ b/src/librustc_back/target/arm_linux_androideabi.rs
@@ -8,14 +8,14 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use target::Target;
+use target::{Target, TargetResult};
 
-pub fn target() -> Target {
+pub fn target() -> TargetResult {
     let mut base = super::android_base::opts();
     base.features = "+v7,+vfp3,+d16".to_string();
     base.max_atomic_width = 64;
 
-    Target {
+    Ok(Target {
         llvm_target: "arm-linux-androideabi".to_string(),
         target_endian: "little".to_string(),
         target_pointer_width: "32".to_string(),
@@ -25,5 +25,5 @@ pub fn target() -> Target {
         target_env: "".to_string(),
         target_vendor: "unknown".to_string(),
         options: base,
-    }
+    })
 }
diff --git a/src/librustc_back/target/arm_unknown_linux_gnueabi.rs b/src/librustc_back/target/arm_unknown_linux_gnueabi.rs
index 60c4a7c3c90ce..e666a8460e5ea 100644
--- a/src/librustc_back/target/arm_unknown_linux_gnueabi.rs
+++ b/src/librustc_back/target/arm_unknown_linux_gnueabi.rs
@@ -8,12 +8,12 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use target::{Target, TargetOptions};
+use target::{Target, TargetOptions, TargetResult};
 
-pub fn target() -> Target {
+pub fn target() -> TargetResult {
     let mut base = super::linux_base::opts();
     base.max_atomic_width = 64;
-    Target {
+    Ok(Target {
         llvm_target: "arm-unknown-linux-gnueabi".to_string(),
         target_endian: "little".to_string(),
         target_pointer_width: "32".to_string(),
@@ -27,5 +27,5 @@ pub fn target() -> Target {
             features: "+v6".to_string(),
             .. base
         },
-    }
+    })
 }
diff --git a/src/librustc_back/target/arm_unknown_linux_gnueabihf.rs b/src/librustc_back/target/arm_unknown_linux_gnueabihf.rs
index 72128e30641c6..d65c89abc2064 100644
--- a/src/librustc_back/target/arm_unknown_linux_gnueabihf.rs
+++ b/src/librustc_back/target/arm_unknown_linux_gnueabihf.rs
@@ -8,12 +8,12 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use target::{Target, TargetOptions};
+use target::{Target, TargetOptions, TargetResult};
 
-pub fn target() -> Target {
+pub fn target() -> TargetResult {
     let mut base = super::linux_base::opts();
     base.max_atomic_width = 64;
-    Target {
+    Ok(Target {
         llvm_target: "arm-unknown-linux-gnueabihf".to_string(),
         target_endian: "little".to_string(),
         target_pointer_width: "32".to_string(),
@@ -27,5 +27,5 @@ pub fn target() -> Target {
             features: "+v6,+vfp2".to_string(),
             .. base
         }
-    }
+    })
 }
diff --git a/src/librustc_back/target/armv7_apple_ios.rs b/src/librustc_back/target/armv7_apple_ios.rs
index a2486a1330a53..a806204d0a6bc 100644
--- a/src/librustc_back/target/armv7_apple_ios.rs
+++ b/src/librustc_back/target/armv7_apple_ios.rs
@@ -8,11 +8,12 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use target::{Target, TargetOptions};
+use target::{Target, TargetOptions, TargetResult};
 use super::apple_ios_base::{opts, Arch};
 
-pub fn target() -> Target {
-    Target {
+pub fn target() -> TargetResult {
+    let base = try!(opts(Arch::Armv7));
+    Ok(Target {
         llvm_target: "armv7-apple-ios".to_string(),
         target_endian: "little".to_string(),
         target_pointer_width: "32".to_string(),
@@ -24,7 +25,7 @@ pub fn target() -> Target {
         options: TargetOptions {
             features: "+v7,+vfp3,+neon".to_string(),
             max_atomic_width: 64,
-            .. opts(Arch::Armv7)
+            .. base
         }
-    }
+    })
 }
diff --git a/src/librustc_back/target/armv7_linux_androideabi.rs b/src/librustc_back/target/armv7_linux_androideabi.rs
index fd8f35da16f61..1c59262e04198 100644
--- a/src/librustc_back/target/armv7_linux_androideabi.rs
+++ b/src/librustc_back/target/armv7_linux_androideabi.rs
@@ -8,14 +8,14 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use target::Target;
+use target::{Target, TargetResult};
 
-pub fn target() -> Target {
+pub fn target() -> TargetResult {
     let mut base = super::android_base::opts();
     base.features = "+v7,+thumb2,+vfp3,+d16".to_string();
     base.max_atomic_width = 64;
 
-    Target {
+    Ok(Target {
         llvm_target: "armv7-none-linux-android".to_string(),
         target_endian: "little".to_string(),
         target_pointer_width: "32".to_string(),
@@ -25,5 +25,5 @@ pub fn target() -> Target {
         target_env: "".to_string(),
         target_vendor: "unknown".to_string(),
         options: base,
-    }
+    })
 }
diff --git a/src/librustc_back/target/armv7_unknown_linux_gnueabihf.rs b/src/librustc_back/target/armv7_unknown_linux_gnueabihf.rs
index 7bcca3a3934be..52269f0cd4a08 100644
--- a/src/librustc_back/target/armv7_unknown_linux_gnueabihf.rs
+++ b/src/librustc_back/target/armv7_unknown_linux_gnueabihf.rs
@@ -8,11 +8,11 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use target::{Target, TargetOptions};
+use target::{Target, TargetOptions, TargetResult};
 
-pub fn target() -> Target {
+pub fn target() -> TargetResult {
     let base = super::linux_base::opts();
-    Target {
+    Ok(Target {
         llvm_target: "armv7-unknown-linux-gnueabihf".to_string(),
         target_endian: "little".to_string(),
         target_pointer_width: "32".to_string(),
@@ -28,6 +28,6 @@ pub fn target() -> Target {
             max_atomic_width: 64,
             .. base
         }
-    }
+    })
 }
 
diff --git a/src/librustc_back/target/armv7s_apple_ios.rs b/src/librustc_back/target/armv7s_apple_ios.rs
index e5379aa1b42cd..aaa3570fa62ee 100644
--- a/src/librustc_back/target/armv7s_apple_ios.rs
+++ b/src/librustc_back/target/armv7s_apple_ios.rs
@@ -8,11 +8,12 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use target::{Target, TargetOptions};
+use target::{Target, TargetOptions, TargetResult};
 use super::apple_ios_base::{opts, Arch};
 
-pub fn target() -> Target {
-    Target {
+pub fn target() -> TargetResult {
+    let base = try!(opts(Arch::Armv7s));
+    Ok(Target {
         llvm_target: "armv7s-apple-ios".to_string(),
         target_endian: "little".to_string(),
         target_pointer_width: "32".to_string(),
@@ -24,7 +25,7 @@ pub fn target() -> Target {
         options: TargetOptions {
             features: "+v7,+vfp4,+neon".to_string(),
             max_atomic_width: 64,
-            .. opts(Arch::Armv7s)
+            .. base
         }
-    }
+    })
 }
diff --git a/src/librustc_back/target/asmjs_unknown_emscripten.rs b/src/librustc_back/target/asmjs_unknown_emscripten.rs
index e6200177944bb..07eb191471c46 100644
--- a/src/librustc_back/target/asmjs_unknown_emscripten.rs
+++ b/src/librustc_back/target/asmjs_unknown_emscripten.rs
@@ -10,7 +10,7 @@
 
 use super::{Target, TargetOptions};
 
-pub fn target() -> Target {
+pub fn target() -> Result<Target, String> {
     let opts = TargetOptions {
         linker: "emcc".to_string(),
         ar: "emar".to_string(),
@@ -25,7 +25,7 @@ pub fn target() -> Target {
         max_atomic_width: 32,
         .. Default::default()
     };
-    Target {
+    Ok(Target {
         llvm_target: "asmjs-unknown-emscripten".to_string(),
         target_endian: "little".to_string(),
         target_pointer_width: "32".to_string(),
@@ -35,5 +35,5 @@ pub fn target() -> Target {
         data_layout: "e-p:32:32-i64:64-v128:32:128-n32-S128".to_string(),
         arch: "asmjs".to_string(),
         options: opts,
-    }
+    })
 }
diff --git a/src/librustc_back/target/i386_apple_ios.rs b/src/librustc_back/target/i386_apple_ios.rs
index cf4020eeb5874..f391d4118ea74 100644
--- a/src/librustc_back/target/i386_apple_ios.rs
+++ b/src/librustc_back/target/i386_apple_ios.rs
@@ -8,11 +8,12 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use target::{Target, TargetOptions};
+use target::{Target, TargetOptions, TargetResult};
 use super::apple_ios_base::{opts, Arch};
 
-pub fn target() -> Target {
-    Target {
+pub fn target() -> TargetResult {
+    let base = try!(opts(Arch::I386));
+    Ok(Target {
         llvm_target: "i386-apple-ios".to_string(),
         target_endian: "little".to_string(),
         target_pointer_width: "32".to_string(),
@@ -23,7 +24,7 @@ pub fn target() -> Target {
         target_vendor: "apple".to_string(),
         options: TargetOptions {
             max_atomic_width: 64,
-            .. opts(Arch::I386)
+            .. base
         }
-    }
+    })
 }
diff --git a/src/librustc_back/target/i586_pc_windows_msvc.rs b/src/librustc_back/target/i586_pc_windows_msvc.rs
index 12bed370eae94..445ee6c412283 100644
--- a/src/librustc_back/target/i586_pc_windows_msvc.rs
+++ b/src/librustc_back/target/i586_pc_windows_msvc.rs
@@ -8,11 +8,11 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use target::Target;
+use target::TargetResult;
 
-pub fn target() -> Target {
-    let mut base = super::i686_pc_windows_msvc::target();
+pub fn target() -> TargetResult {
+    let mut base = try!(super::i686_pc_windows_msvc::target());
     base.options.cpu = "pentium".to_string();
     base.llvm_target = "i586-pc-windows-msvc".to_string();
-    return base
+    Ok(base)
 }
diff --git a/src/librustc_back/target/i586_unknown_linux_gnu.rs b/src/librustc_back/target/i586_unknown_linux_gnu.rs
index 6eb6455638190..1ca8606149bff 100644
--- a/src/librustc_back/target/i586_unknown_linux_gnu.rs
+++ b/src/librustc_back/target/i586_unknown_linux_gnu.rs
@@ -8,11 +8,11 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use target::Target;
+use target::TargetResult;
 
-pub fn target() -> Target {
-    let mut base = super::i686_unknown_linux_gnu::target();
+pub fn target() -> TargetResult {
+    let mut base = try!(super::i686_unknown_linux_gnu::target());
     base.options.cpu = "pentium".to_string();
     base.llvm_target = "i586-unknown-linux-gnu".to_string();
-    return base
+    Ok(base)
 }
diff --git a/src/librustc_back/target/i686_apple_darwin.rs b/src/librustc_back/target/i686_apple_darwin.rs
index 302691e9a5922..4876a3489d470 100644
--- a/src/librustc_back/target/i686_apple_darwin.rs
+++ b/src/librustc_back/target/i686_apple_darwin.rs
@@ -8,15 +8,15 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use target::Target;
+use target::{Target, TargetResult};
 
-pub fn target() -> Target {
+pub fn target() -> TargetResult {
     let mut base = super::apple_base::opts();
     base.cpu = "yonah".to_string();
     base.max_atomic_width = 64;
     base.pre_link_args.push("-m32".to_string());
 
-    Target {
+    Ok(Target {
         llvm_target: "i686-apple-darwin".to_string(),
         target_endian: "little".to_string(),
         target_pointer_width: "32".to_string(),
@@ -26,5 +26,5 @@ pub fn target() -> Target {
         target_env: "".to_string(),
         target_vendor: "apple".to_string(),
         options: base,
-    }
+    })
 }
diff --git a/src/librustc_back/target/i686_linux_android.rs b/src/librustc_back/target/i686_linux_android.rs
index 2376de123980b..1de629238a13c 100644
--- a/src/librustc_back/target/i686_linux_android.rs
+++ b/src/librustc_back/target/i686_linux_android.rs
@@ -8,9 +8,9 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use target::Target;
+use target::{Target, TargetResult};
 
-pub fn target() -> Target {
+pub fn target() -> TargetResult {
     let mut base = super::android_base::opts();
 
     base.max_atomic_width = 64;
@@ -19,7 +19,7 @@ pub fn target() -> Target {
     base.cpu = "pentiumpro".to_string();
     base.features = "+mmx,+sse,+sse2,+sse3,+ssse3".to_string();
 
-    Target {
+    Ok(Target {
         llvm_target: "i686-linux-android".to_string(),
         target_endian: "little".to_string(),
         target_pointer_width: "32".to_string(),
@@ -29,5 +29,5 @@ pub fn target() -> Target {
         target_env: "".to_string(),
         target_vendor: "unknown".to_string(),
         options: base,
-    }
+    })
 }
diff --git a/src/librustc_back/target/i686_pc_windows_gnu.rs b/src/librustc_back/target/i686_pc_windows_gnu.rs
index c2cc624c9f9e6..2c19b8109c362 100644
--- a/src/librustc_back/target/i686_pc_windows_gnu.rs
+++ b/src/librustc_back/target/i686_pc_windows_gnu.rs
@@ -8,9 +8,9 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use target::Target;
+use target::{Target, TargetResult};
 
-pub fn target() -> Target {
+pub fn target() -> TargetResult {
     let mut base = super::windows_base::opts();
     base.cpu = "pentium4".to_string();
     base.max_atomic_width = 64;
@@ -19,7 +19,7 @@ pub fn target() -> Target {
     // space available to x86 Windows binaries on x86_64.
     base.pre_link_args.push("-Wl,--large-address-aware".to_string());
 
-    Target {
+    Ok(Target {
         llvm_target: "i686-pc-windows-gnu".to_string(),
         target_endian: "little".to_string(),
         target_pointer_width: "32".to_string(),
@@ -29,5 +29,5 @@ pub fn target() -> Target {
         target_env: "gnu".to_string(),
         target_vendor: "pc".to_string(),
         options: base,
-    }
+    })
 }
diff --git a/src/librustc_back/target/i686_pc_windows_msvc.rs b/src/librustc_back/target/i686_pc_windows_msvc.rs
index 8c1bacc280767..cb02fcc308c2d 100644
--- a/src/librustc_back/target/i686_pc_windows_msvc.rs
+++ b/src/librustc_back/target/i686_pc_windows_msvc.rs
@@ -8,9 +8,9 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use target::Target;
+use target::{Target, TargetResult};
 
-pub fn target() -> Target {
+pub fn target() -> TargetResult {
     let mut base = super::windows_msvc_base::opts();
     base.cpu = "pentium4".to_string();
     base.max_atomic_width = 64;
@@ -24,7 +24,7 @@ pub fn target() -> Target {
     // https://msdn.microsoft.com/en-us/library/9a89h429.aspx
     base.pre_link_args.push("/SAFESEH".to_string());
 
-    Target {
+    Ok(Target {
         llvm_target: "i686-pc-windows-msvc".to_string(),
         target_endian: "little".to_string(),
         target_pointer_width: "32".to_string(),
@@ -34,5 +34,5 @@ pub fn target() -> Target {
         target_env: "msvc".to_string(),
         target_vendor: "pc".to_string(),
         options: base,
-    }
+    })
 }
diff --git a/src/librustc_back/target/i686_unknown_dragonfly.rs b/src/librustc_back/target/i686_unknown_dragonfly.rs
index 6446ac45f7d6e..f96ec004b481e 100644
--- a/src/librustc_back/target/i686_unknown_dragonfly.rs
+++ b/src/librustc_back/target/i686_unknown_dragonfly.rs
@@ -8,15 +8,15 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use target::Target;
+use target::{Target, TargetResult};
 
-pub fn target() -> Target {
+pub fn target() -> TargetResult {
     let mut base = super::dragonfly_base::opts();
     base.cpu = "pentium4".to_string();
     base.max_atomic_width = 64;
     base.pre_link_args.push("-m32".to_string());
 
-    Target {
+    Ok(Target {
         llvm_target: "i686-unknown-dragonfly".to_string(),
         target_endian: "little".to_string(),
         target_pointer_width: "32".to_string(),
@@ -26,5 +26,5 @@ pub fn target() -> Target {
         target_env: "".to_string(),
         target_vendor: "unknown".to_string(),
         options: base,
-    }
+    })
 }
diff --git a/src/librustc_back/target/i686_unknown_freebsd.rs b/src/librustc_back/target/i686_unknown_freebsd.rs
index a7903d5db6413..3489ecfe614d9 100644
--- a/src/librustc_back/target/i686_unknown_freebsd.rs
+++ b/src/librustc_back/target/i686_unknown_freebsd.rs
@@ -8,15 +8,15 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use target::Target;
+use target::{Target, TargetResult};
 
-pub fn target() -> Target {
+pub fn target() -> TargetResult {
     let mut base = super::freebsd_base::opts();
     base.cpu = "pentium4".to_string();
     base.max_atomic_width = 64;
     base.pre_link_args.push("-m32".to_string());
 
-    Target {
+    Ok(Target {
         llvm_target: "i686-unknown-freebsd".to_string(),
         target_endian: "little".to_string(),
         target_pointer_width: "32".to_string(),
@@ -26,5 +26,5 @@ pub fn target() -> Target {
         target_env: "".to_string(),
         target_vendor: "unknown".to_string(),
         options: base,
-    }
+    })
 }
diff --git a/src/librustc_back/target/i686_unknown_linux_gnu.rs b/src/librustc_back/target/i686_unknown_linux_gnu.rs
index 7813d5570762d..f2e865c015e35 100644
--- a/src/librustc_back/target/i686_unknown_linux_gnu.rs
+++ b/src/librustc_back/target/i686_unknown_linux_gnu.rs
@@ -8,15 +8,15 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use target::Target;
+use target::{Target, TargetResult};
 
-pub fn target() -> Target {
+pub fn target() -> TargetResult {
     let mut base = super::linux_base::opts();
     base.cpu = "pentium4".to_string();
     base.max_atomic_width = 64;
     base.pre_link_args.push("-m32".to_string());
 
-    Target {
+    Ok(Target {
         llvm_target: "i686-unknown-linux-gnu".to_string(),
         target_endian: "little".to_string(),
         target_pointer_width: "32".to_string(),
@@ -26,5 +26,5 @@ pub fn target() -> Target {
         target_env: "gnu".to_string(),
         target_vendor: "unknown".to_string(),
         options: base,
-    }
+    })
 }
diff --git a/src/librustc_back/target/i686_unknown_linux_musl.rs b/src/librustc_back/target/i686_unknown_linux_musl.rs
index 5274429583742..a0a8de46e2f59 100644
--- a/src/librustc_back/target/i686_unknown_linux_musl.rs
+++ b/src/librustc_back/target/i686_unknown_linux_musl.rs
@@ -8,16 +8,16 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use target::Target;
+use target::{Target, TargetResult};
 
-pub fn target() -> Target {
+pub fn target() -> TargetResult {
     let mut base = super::linux_musl_base::opts();
     base.cpu = "pentium4".to_string();
     base.max_atomic_width = 64;
     base.pre_link_args.push("-m32".to_string());
     base.pre_link_args.push("-Wl,-melf_i386".to_string());
 
-    Target {
+    Ok(Target {
         llvm_target: "i686-unknown-linux-musl".to_string(),
         target_endian: "little".to_string(),
         target_pointer_width: "32".to_string(),
@@ -27,5 +27,5 @@ pub fn target() -> Target {
         target_env: "musl".to_string(),
         target_vendor: "unknown".to_string(),
         options: base,
-    }
+    })
 }
diff --git a/src/librustc_back/target/le32_unknown_nacl.rs b/src/librustc_back/target/le32_unknown_nacl.rs
index f4f0262d476da..25132f8a044d6 100644
--- a/src/librustc_back/target/le32_unknown_nacl.rs
+++ b/src/librustc_back/target/le32_unknown_nacl.rs
@@ -8,9 +8,9 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use super::{Target, TargetOptions};
+use super::{Target, TargetOptions, TargetResult};
 
-pub fn target() -> Target {
+pub fn target() -> TargetResult {
     let opts = TargetOptions {
         linker: "pnacl-clang".to_string(),
         ar: "pnacl-ar".to_string(),
@@ -28,7 +28,7 @@ pub fn target() -> Target {
         max_atomic_width: 32,
         .. Default::default()
     };
-    Target {
+    Ok(Target {
         llvm_target: "le32-unknown-nacl".to_string(),
         target_endian: "little".to_string(),
         target_pointer_width: "32".to_string(),
@@ -38,5 +38,5 @@ pub fn target() -> Target {
         data_layout: "e-i64:64:64-p:32:32:32-v128:32:32".to_string(),
         arch: "le32".to_string(),
         options: opts,
-    }
+    })
 }
diff --git a/src/librustc_back/target/mips_unknown_linux_gnu.rs b/src/librustc_back/target/mips_unknown_linux_gnu.rs
index ceb17e53a5552..ab967f6b40fbe 100644
--- a/src/librustc_back/target/mips_unknown_linux_gnu.rs
+++ b/src/librustc_back/target/mips_unknown_linux_gnu.rs
@@ -8,10 +8,10 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use target::{Target, TargetOptions};
+use target::{Target, TargetOptions, TargetResult};
 
-pub fn target() -> Target {
-    Target {
+pub fn target() -> TargetResult {
+    Ok(Target {
         llvm_target: "mips-unknown-linux-gnu".to_string(),
         target_endian: "big".to_string(),
         target_pointer_width: "32".to_string(),
@@ -26,5 +26,5 @@ pub fn target() -> Target {
             max_atomic_width: 32,
             ..super::linux_base::opts()
         },
-    }
+    })
 }
diff --git a/src/librustc_back/target/mips_unknown_linux_musl.rs b/src/librustc_back/target/mips_unknown_linux_musl.rs
index 35366659d581f..4a69bce53bc97 100644
--- a/src/librustc_back/target/mips_unknown_linux_musl.rs
+++ b/src/librustc_back/target/mips_unknown_linux_musl.rs
@@ -8,10 +8,10 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use target::{Target, TargetOptions};
+use target::{Target, TargetOptions, TargetResult};
 
-pub fn target() -> Target {
-    Target {
+pub fn target() -> TargetResult {
+    Ok(Target {
         llvm_target: "mips-unknown-linux-musl".to_string(),
         target_endian: "big".to_string(),
         target_pointer_width: "32".to_string(),
@@ -26,5 +26,5 @@ pub fn target() -> Target {
             max_atomic_width: 32,
             ..super::linux_base::opts()
         }
-    }
+    })
 }
diff --git a/src/librustc_back/target/mipsel_unknown_linux_gnu.rs b/src/librustc_back/target/mipsel_unknown_linux_gnu.rs
index ac1536b3d009b..b66fb62cd591e 100644
--- a/src/librustc_back/target/mipsel_unknown_linux_gnu.rs
+++ b/src/librustc_back/target/mipsel_unknown_linux_gnu.rs
@@ -8,10 +8,10 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use target::{Target, TargetOptions};
+use target::{Target, TargetOptions, TargetResult};
 
-pub fn target() -> Target {
-    Target {
+pub fn target() -> TargetResult {
+    Ok(Target {
         llvm_target: "mipsel-unknown-linux-gnu".to_string(),
         target_endian: "little".to_string(),
         target_pointer_width: "32".to_string(),
@@ -27,5 +27,5 @@ pub fn target() -> Target {
             max_atomic_width: 32,
             ..super::linux_base::opts()
         },
-    }
+    })
 }
diff --git a/src/librustc_back/target/mipsel_unknown_linux_musl.rs b/src/librustc_back/target/mipsel_unknown_linux_musl.rs
index a9ea52c427862..24d1a66ec2d2f 100644
--- a/src/librustc_back/target/mipsel_unknown_linux_musl.rs
+++ b/src/librustc_back/target/mipsel_unknown_linux_musl.rs
@@ -8,10 +8,10 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use target::{Target, TargetOptions};
+use target::{Target, TargetOptions, TargetResult};
 
-pub fn target() -> Target {
-    Target {
+pub fn target() -> TargetResult {
+    Ok(Target {
         llvm_target: "mipsel-unknown-linux-musl".to_string(),
         target_endian: "little".to_string(),
         target_pointer_width: "32".to_string(),
@@ -26,5 +26,5 @@ pub fn target() -> Target {
             max_atomic_width: 32,
             ..super::linux_base::opts()
         }
-    }
+    })
 }
diff --git a/src/librustc_back/target/mod.rs b/src/librustc_back/target/mod.rs
index 99bc26848025e..f5314809228b5 100644
--- a/src/librustc_back/target/mod.rs
+++ b/src/librustc_back/target/mod.rs
@@ -44,7 +44,8 @@
 //! the target's settings, though `target-feature` and `link-args` will *add*
 //! to the list specified by the target, rather than replace.
 
-use serialize::json::Json;
+use serialize::json::{Json, ToJson};
+use std::collections::BTreeMap;
 use std::default::Default;
 use std::io::prelude::*;
 use syntax::abi::Abi;
@@ -63,26 +64,62 @@ mod solaris_base;
 mod windows_base;
 mod windows_msvc_base;
 
+pub type TargetResult = Result<Target, String>;
+
 macro_rules! supported_targets {
     ( $(($triple:expr, $module:ident)),+ ) => (
         $(mod $module;)*
 
         /// List of supported targets
-        pub const TARGETS: &'static [&'static str] = &[$($triple),*];
+        const TARGETS: &'static [&'static str] = &[$($triple),*];
 
-        fn load_specific(target: &str) -> Option<Target> {
+        fn load_specific(target: &str) -> TargetResult {
             match target {
                 $(
                     $triple => {
-                        let mut t = $module::target();
+                        let mut t = try!($module::target());
                         t.options.is_builtin = true;
+
+                        // round-trip through the JSON parser to ensure at
+                        // run-time that the parser works correctly
+                        t = try!(Target::from_json(t.to_json()));
                         debug!("Got builtin target: {:?}", t);
-                        Some(t)
+                        Ok(t)
                     },
                 )+
-                _ => None
+                _ => Err(format!("Unable to find target: {}", target))
             }
         }
+
+        pub fn get_targets() -> Box<Iterator<Item=String>> {
+            Box::new(TARGETS.iter().filter_map(|t| -> Option<String> {
+                load_specific(t)
+                    .map(|t| t.llvm_target)
+                    .ok()
+            }))
+        }
+
+        #[cfg(test)]
+        mod test_json_encode_decode {
+            use serialize::json::ToJson;
+            use super::Target;
+            $(use super::$module;)*
+
+            $(
+                #[test]
+                fn $module() {
+                    // Grab the TargetResult struct. If we successfully retrieved
+                    // a Target, then the test JSON encoding/decoding can run for this
+                    // Target on this testing platform (i.e., checking the iOS targets
+                    // only on a Mac test platform).
+                    let _ = $module::target().map(|original| {
+                        let as_json = original.to_json();
+                        let parsed = Target::from_json(as_json).unwrap();
+                        assert_eq!(original, parsed);
+                    });
+                }
+            )*
+        }
     )
 }
 
@@ -145,7 +182,7 @@ supported_targets! {
 /// Everything `rustc` knows about how to compile for a specific target.
 ///
 /// Every field here must be specified, and has no default value.
-#[derive(Clone, Debug)]
+#[derive(PartialEq, Clone, Debug)]
 pub struct Target {
     /// Target triple to pass to LLVM.
     pub llvm_target: String,
@@ -172,7 +209,7 @@ pub struct Target {
 ///
 /// This has an implementation of `Default`, see each field for what the default is. In general,
 /// these try to take "minimal defaults" that don't assume anything about the runtime they run in.
-#[derive(Clone, Debug)]
+#[derive(PartialEq, Clone, Debug)]
 pub struct TargetOptions {
     /// Whether the target is built-in or loaded from a custom target specification.
     pub is_builtin: bool,
@@ -363,16 +400,21 @@ impl Target {
     }
 
     /// Load a target descriptor from a JSON object.
-    pub fn from_json(obj: Json) -> Target {
-        // this is 1. ugly, 2. error prone.
+    pub fn from_json(obj: Json) -> TargetResult {
+        // While ugly, this code must remain this way to retain
+        // compatibility with existing JSON fields and the internal
+        // expected naming of the Target and TargetOptions structs.
+        // To ensure compatibility is retained, the built-in targets
+        // are round-tripped through this code to catch cases where
+        // the JSON parser is not updated to match the structs.
 
         let get_req_field = |name: &str| {
             match obj.find(name)
                      .map(|s| s.as_string())
                      .and_then(|os| os.map(|s| s.to_string())) {
-                Some(val) => val,
+                Some(val) => Ok(val),
                 None => {
-                    panic!("Field {} in target specification is required", name)
+                    return Err(format!("Field {} in target specification is required", name))
                 }
             }
         };
@@ -384,12 +426,12 @@ impl Target {
         };
 
         let mut base = Target {
-            llvm_target: get_req_field("llvm-target"),
-            target_endian: get_req_field("target-endian"),
-            target_pointer_width: get_req_field("target-pointer-width"),
-            data_layout: get_req_field("data-layout"),
-            arch: get_req_field("arch"),
-            target_os: get_req_field("os"),
+            llvm_target: try!(get_req_field("llvm-target")),
+            target_endian: try!(get_req_field("target-endian")),
+            target_pointer_width: try!(get_req_field("target-pointer-width")),
+            data_layout: try!(get_req_field("data-layout")),
+            arch: try!(get_req_field("arch")),
+            target_os: try!(get_req_field("os")),
             target_env: get_opt_field("env", ""),
             target_vendor: get_opt_field("vendor", "unknown"),
             options: Default::default(),
@@ -434,38 +476,50 @@ impl Target {
             } );
         }
 
-        key!(cpu);
-        key!(ar);
+        key!(is_builtin, bool);
         key!(linker);
+        key!(ar);
+        key!(pre_link_args, list);
+        key!(pre_link_objects_exe, list);
+        key!(pre_link_objects_dll, list);
+        key!(late_link_args, list);
+        key!(post_link_objects, list);
+        key!(post_link_args, list);
+        key!(cpu);
+        key!(features);
+        key!(dynamic_linking, bool);
+        key!(executables, bool);
         key!(relocation_model);
         key!(code_model);
+        key!(disable_redzone, bool);
+        key!(eliminate_frame_pointer, bool);
+        key!(function_sections, bool);
         key!(dll_prefix);
         key!(dll_suffix);
         key!(exe_suffix);
         key!(staticlib_prefix);
         key!(staticlib_suffix);
-        key!(features);
-        key!(dynamic_linking, bool);
-        key!(executables, bool);
-        key!(disable_redzone, bool);
-        key!(eliminate_frame_pointer, bool);
-        key!(function_sections, bool);
         key!(target_family, optional);
         key!(is_like_osx, bool);
+        key!(is_like_solaris, bool);
         key!(is_like_windows, bool);
         key!(is_like_msvc, bool);
+        key!(is_like_android, bool);
         key!(linker_is_gnu, bool);
         key!(has_rpath, bool);
         key!(no_compiler_rt, bool);
         key!(no_default_libraries, bool);
-        key!(pre_link_args, list);
-        key!(post_link_args, list);
+        key!(position_independent_executables, bool);
         key!(archive_format);
         key!(allow_asm, bool);
         key!(custom_unwind_resume, bool);
+        key!(lib_allocation_crate);
+        key!(exe_allocation_crate);
+        key!(has_elf_tls, bool);
+        key!(obj_is_bitcode, bool);
         key!(max_atomic_width, u64);
 
-        base
+        Ok(base)
     }
 
     /// Search RUST_TARGET_PATH for a JSON file specifying the given target
@@ -488,10 +542,10 @@ impl Target {
             f.read_to_end(&mut contents).map_err(|e| e.to_string())?;
             let obj = json::from_reader(&mut &contents[..])
                            .map_err(|e| e.to_string())?;
-            Ok(Target::from_json(obj))
+            Target::from_json(obj)
         }
 
-        if let Some(t) = load_specific(target) {
+        if let Ok(t) = load_specific(target) {
             return Ok(t)
         }
 
@@ -523,6 +577,94 @@ impl Target {
     }
 }
 
+impl ToJson for Target {
+    fn to_json(&self) -> Json {
+        let mut d = BTreeMap::new();
+        let default: TargetOptions = Default::default();
+
+        macro_rules! target_val {
+            ($attr:ident) => ( {
+                let name = (stringify!($attr)).replace("_", "-");
+                d.insert(name.to_string(), self.$attr.to_json());
+            } );
+            ($attr:ident, $key_name:expr) => ( {
+                let name = $key_name;
+                d.insert(name.to_string(), self.$attr.to_json());
+            } );
+        }
+
+        macro_rules! target_option_val {
+            ($attr:ident) => ( {
+                let name = (stringify!($attr)).replace("_", "-");
+                if default.$attr != self.options.$attr {
+                    d.insert(name.to_string(), self.options.$attr.to_json());
+                }
+            } );
+            ($attr:ident, $key_name:expr) => ( {
+                let name = $key_name;
+                if default.$attr != self.options.$attr {
+                    d.insert(name.to_string(), self.options.$attr.to_json());
+                }
+            } );
+        }
+
+        target_val!(llvm_target);
+        target_val!(target_endian);
+        target_val!(target_pointer_width);
+        target_val!(arch);
+        target_val!(target_os, "os");
+        target_val!(target_env, "env");
+        target_val!(target_vendor, "vendor");
+        target_val!(arch);
+        target_val!(data_layout);
+
+        target_option_val!(is_builtin);
+        target_option_val!(linker);
+        target_option_val!(ar);
+        target_option_val!(pre_link_args);
+        target_option_val!(pre_link_objects_exe);
+        target_option_val!(pre_link_objects_dll);
+        target_option_val!(late_link_args);
+        target_option_val!(post_link_objects);
+        target_option_val!(post_link_args);
+        target_option_val!(cpu);
+        target_option_val!(features);
+        target_option_val!(dynamic_linking);
+        target_option_val!(executables);
+        target_option_val!(relocation_model);
+        target_option_val!(code_model);
+        target_option_val!(disable_redzone);
+        target_option_val!(eliminate_frame_pointer);
+        target_option_val!(function_sections);
+        target_option_val!(dll_prefix);
+        target_option_val!(dll_suffix);
+        target_option_val!(exe_suffix);
+        target_option_val!(staticlib_prefix);
+        target_option_val!(staticlib_suffix);
+        target_option_val!(target_family);
+        target_option_val!(is_like_osx);
+        target_option_val!(is_like_solaris);
+        target_option_val!(is_like_windows);
+        target_option_val!(is_like_msvc);
+        target_option_val!(is_like_android);
+        target_option_val!(linker_is_gnu);
+        target_option_val!(has_rpath);
+        target_option_val!(no_compiler_rt);
+        target_option_val!(no_default_libraries);
+        target_option_val!(position_independent_executables);
+        target_option_val!(archive_format);
+        target_option_val!(allow_asm);
+        target_option_val!(custom_unwind_resume);
+        target_option_val!(lib_allocation_crate);
+        target_option_val!(exe_allocation_crate);
+        target_option_val!(has_elf_tls);
+        target_option_val!(obj_is_bitcode);
+        target_option_val!(max_atomic_width);
+
+        Json::Object(d)
+    }
+}
+
 fn maybe_jemalloc() -> String {
     if cfg!(feature = "jemalloc") {
         "alloc_jemalloc".to_string()
diff --git a/src/librustc_back/target/powerpc64_unknown_linux_gnu.rs b/src/librustc_back/target/powerpc64_unknown_linux_gnu.rs
index be4be8e6fc964..1c04e763417c4 100644
--- a/src/librustc_back/target/powerpc64_unknown_linux_gnu.rs
+++ b/src/librustc_back/target/powerpc64_unknown_linux_gnu.rs
@@ -8,15 +8,15 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use target::Target;
+use target::{Target, TargetResult};
 
-pub fn target() -> Target {
+pub fn target() -> TargetResult {
     let mut base = super::linux_base::opts();
     base.cpu = "ppc64".to_string();
     base.pre_link_args.push("-m64".to_string());
     base.max_atomic_width = 64;
 
-    Target {
+    Ok(Target {
         llvm_target: "powerpc64-unknown-linux-gnu".to_string(),
         target_endian: "big".to_string(),
         target_pointer_width: "64".to_string(),
@@ -26,5 +26,5 @@ pub fn target() -> Target {
         target_env: "gnu".to_string(),
         target_vendor: "unknown".to_string(),
         options: base,
-    }
+    })
 }
diff --git a/src/librustc_back/target/powerpc64le_unknown_linux_gnu.rs b/src/librustc_back/target/powerpc64le_unknown_linux_gnu.rs
index b0a81ce7ec501..906e28d2f20cb 100644
--- a/src/librustc_back/target/powerpc64le_unknown_linux_gnu.rs
+++ b/src/librustc_back/target/powerpc64le_unknown_linux_gnu.rs
@@ -8,15 +8,15 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use target::Target;
+use target::{Target, TargetResult};
 
-pub fn target() -> Target {
+pub fn target() -> TargetResult {
     let mut base = super::linux_base::opts();
     base.cpu = "ppc64le".to_string();
     base.pre_link_args.push("-m64".to_string());
     base.max_atomic_width = 64;
 
-    Target {
+    Ok(Target {
         llvm_target: "powerpc64le-unknown-linux-gnu".to_string(),
         target_endian: "little".to_string(),
         target_pointer_width: "64".to_string(),
@@ -26,5 +26,5 @@ pub fn target() -> Target {
         target_env: "gnu".to_string(),
         target_vendor: "unknown".to_string(),
         options: base,
-    }
+    })
 }
diff --git a/src/librustc_back/target/powerpc_unknown_linux_gnu.rs b/src/librustc_back/target/powerpc_unknown_linux_gnu.rs
index aea57dc4b7f95..aebf9cd68717d 100644
--- a/src/librustc_back/target/powerpc_unknown_linux_gnu.rs
+++ b/src/librustc_back/target/powerpc_unknown_linux_gnu.rs
@@ -8,14 +8,14 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use target::Target;
+use target::{Target, TargetResult};
 
-pub fn target() -> Target {
+pub fn target() -> TargetResult {
     let mut base = super::linux_base::opts();
     base.pre_link_args.push("-m32".to_string());
     base.max_atomic_width = 32;
 
-    Target {
+    Ok(Target {
         llvm_target: "powerpc-unknown-linux-gnu".to_string(),
         target_endian: "big".to_string(),
         target_pointer_width: "32".to_string(),
@@ -25,5 +25,5 @@ pub fn target() -> Target {
         target_env: "gnu".to_string(),
         target_vendor: "unknown".to_string(),
         options: base,
-    }
+    })
 }
diff --git a/src/librustc_back/target/x86_64_apple_darwin.rs b/src/librustc_back/target/x86_64_apple_darwin.rs
index 5542c9120a402..65e4b1400fcf8 100644
--- a/src/librustc_back/target/x86_64_apple_darwin.rs
+++ b/src/librustc_back/target/x86_64_apple_darwin.rs
@@ -8,16 +8,16 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use target::Target;
+use target::{Target, TargetResult};
 
-pub fn target() -> Target {
+pub fn target() -> TargetResult {
     let mut base = super::apple_base::opts();
     base.cpu = "core2".to_string();
     base.max_atomic_width = 128; // core2 support cmpxchg16b
     base.eliminate_frame_pointer = false;
     base.pre_link_args.push("-m64".to_string());
 
-    Target {
+    Ok(Target {
         llvm_target: "x86_64-apple-darwin".to_string(),
         target_endian: "little".to_string(),
         target_pointer_width: "64".to_string(),
@@ -27,5 +27,5 @@ pub fn target() -> Target {
         target_env: "".to_string(),
         target_vendor: "apple".to_string(),
         options: base,
-    }
+    })
 }
diff --git a/src/librustc_back/target/x86_64_apple_ios.rs b/src/librustc_back/target/x86_64_apple_ios.rs
index 8638241f8610b..4afc9bcb946c2 100644
--- a/src/librustc_back/target/x86_64_apple_ios.rs
+++ b/src/librustc_back/target/x86_64_apple_ios.rs
@@ -8,11 +8,12 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use target::{Target, TargetOptions};
+use target::{Target, TargetOptions, TargetResult};
 use super::apple_ios_base::{opts, Arch};
 
-pub fn target() -> Target {
-    Target {
+pub fn target() -> TargetResult {
+    let base = try!(opts(Arch::X86_64));
+    Ok(Target {
         llvm_target: "x86_64-apple-ios".to_string(),
         target_endian: "little".to_string(),
         target_pointer_width: "64".to_string(),
@@ -23,7 +24,7 @@ pub fn target() -> Target {
         target_vendor: "apple".to_string(),
         options: TargetOptions {
             max_atomic_width: 64,
-            .. opts(Arch::X86_64)
+            .. base
         }
-    }
+    })
 }
diff --git a/src/librustc_back/target/x86_64_pc_windows_gnu.rs b/src/librustc_back/target/x86_64_pc_windows_gnu.rs
index e243054d0230e..086e0e6bf4fe7 100644
--- a/src/librustc_back/target/x86_64_pc_windows_gnu.rs
+++ b/src/librustc_back/target/x86_64_pc_windows_gnu.rs
@@ -8,15 +8,15 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use target::Target;
+use target::{Target, TargetResult};
 
-pub fn target() -> Target {
+pub fn target() -> TargetResult {
     let mut base = super::windows_base::opts();
     base.cpu = "x86-64".to_string();
     base.pre_link_args.push("-m64".to_string());
     base.max_atomic_width = 64;
 
-    Target {
+    Ok(Target {
         llvm_target: "x86_64-pc-windows-gnu".to_string(),
         target_endian: "little".to_string(),
         target_pointer_width: "64".to_string(),
@@ -26,5 +26,5 @@ pub fn target() -> Target {
         target_env: "gnu".to_string(),
         target_vendor: "pc".to_string(),
         options: base,
-    }
+    })
 }
diff --git a/src/librustc_back/target/x86_64_pc_windows_msvc.rs b/src/librustc_back/target/x86_64_pc_windows_msvc.rs
index a23a807a0257e..064f06e9b31d6 100644
--- a/src/librustc_back/target/x86_64_pc_windows_msvc.rs
+++ b/src/librustc_back/target/x86_64_pc_windows_msvc.rs
@@ -8,14 +8,14 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use target::Target;
+use target::{Target, TargetResult};
 
-pub fn target() -> Target {
+pub fn target() -> TargetResult {
     let mut base = super::windows_msvc_base::opts();
     base.cpu = "x86-64".to_string();
     base.max_atomic_width = 64;
 
-    Target {
+    Ok(Target {
         llvm_target: "x86_64-pc-windows-msvc".to_string(),
         target_endian: "little".to_string(),
         target_pointer_width: "64".to_string(),
@@ -25,5 +25,5 @@ pub fn target() -> Target {
         target_env: "msvc".to_string(),
         target_vendor: "pc".to_string(),
         options: base,
-    }
+    })
 }
diff --git a/src/librustc_back/target/x86_64_rumprun_netbsd.rs b/src/librustc_back/target/x86_64_rumprun_netbsd.rs
index af5d21c4d93e4..537d15f4603bb 100644
--- a/src/librustc_back/target/x86_64_rumprun_netbsd.rs
+++ b/src/librustc_back/target/x86_64_rumprun_netbsd.rs
@@ -8,9 +8,9 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use target::Target;
+use target::{Target, TargetResult};
 
-pub fn target() -> Target {
+pub fn target() -> TargetResult {
     let mut base = super::netbsd_base::opts();
     base.pre_link_args.push("-m64".to_string());
     base.linker = "x86_64-rumprun-netbsd-gcc".to_string();
@@ -24,7 +24,7 @@ pub fn target() -> Target {
     base.no_default_libraries = false;
     base.exe_allocation_crate = "alloc_system".to_string();
 
-    Target {
+    Ok(Target {
         llvm_target: "x86_64-rumprun-netbsd".to_string(),
         target_endian: "little".to_string(),
         target_pointer_width: "64".to_string(),
@@ -34,5 +34,5 @@ pub fn target() -> Target {
         target_env: "".to_string(),
         target_vendor: "rumprun".to_string(),
         options: base,
-    }
+    })
 }
diff --git a/src/librustc_back/target/x86_64_sun_solaris.rs b/src/librustc_back/target/x86_64_sun_solaris.rs
index 8f2c905cf2ee4..2a1feb937f742 100644
--- a/src/librustc_back/target/x86_64_sun_solaris.rs
+++ b/src/librustc_back/target/x86_64_sun_solaris.rs
@@ -8,15 +8,15 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use target::Target;
+use target::{Target, TargetResult};
 
-pub fn target() -> Target {
+pub fn target() -> TargetResult {
     let mut base = super::solaris_base::opts();
     base.pre_link_args.push("-m64".to_string());
     base.cpu = "x86-64".to_string();
     base.max_atomic_width = 64;
 
-    Target {
+    Ok(Target {
         llvm_target: "x86_64-pc-solaris".to_string(),
         target_endian: "little".to_string(),
         target_pointer_width: "64".to_string(),
@@ -26,5 +26,5 @@ pub fn target() -> Target {
         target_env: "".to_string(),
         target_vendor: "sun".to_string(),
         options: base,
-    }
+    })
 }
diff --git a/src/librustc_back/target/x86_64_unknown_bitrig.rs b/src/librustc_back/target/x86_64_unknown_bitrig.rs
index 87753da540a36..81710b99b80be 100644
--- a/src/librustc_back/target/x86_64_unknown_bitrig.rs
+++ b/src/librustc_back/target/x86_64_unknown_bitrig.rs
@@ -8,14 +8,14 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use target::Target;
+use target::{Target, TargetResult};
 
-pub fn target() -> Target {
+pub fn target() -> TargetResult {
     let mut base = super::bitrig_base::opts();
     base.max_atomic_width = 64;
     base.pre_link_args.push("-m64".to_string());
 
-    Target {
+    Ok(Target {
         llvm_target: "x86_64-unknown-bitrig".to_string(),
         target_endian: "little".to_string(),
         target_pointer_width: "64".to_string(),
@@ -25,5 +25,5 @@ pub fn target() -> Target {
         target_env: "".to_string(),
         target_vendor: "unknown".to_string(),
         options: base,
-    }
+    })
 }
diff --git a/src/librustc_back/target/x86_64_unknown_dragonfly.rs b/src/librustc_back/target/x86_64_unknown_dragonfly.rs
index 2535071f3089c..7e40d49b870ad 100644
--- a/src/librustc_back/target/x86_64_unknown_dragonfly.rs
+++ b/src/librustc_back/target/x86_64_unknown_dragonfly.rs
@@ -8,15 +8,15 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use target::Target;
+use target::{Target, TargetResult};
 
-pub fn target() -> Target {
+pub fn target() -> TargetResult {
     let mut base = super::dragonfly_base::opts();
     base.cpu = "x86-64".to_string();
     base.max_atomic_width = 64;
     base.pre_link_args.push("-m64".to_string());
 
-    Target {
+    Ok(Target {
         llvm_target: "x86_64-unknown-dragonfly".to_string(),
         target_endian: "little".to_string(),
         target_pointer_width: "64".to_string(),
@@ -26,5 +26,5 @@ pub fn target() -> Target {
         target_env: "".to_string(),
         target_vendor: "unknown".to_string(),
         options: base,
-    }
+    })
 }
diff --git a/src/librustc_back/target/x86_64_unknown_freebsd.rs b/src/librustc_back/target/x86_64_unknown_freebsd.rs
index d3ad0578aeb6e..f38cdd4bec55f 100644
--- a/src/librustc_back/target/x86_64_unknown_freebsd.rs
+++ b/src/librustc_back/target/x86_64_unknown_freebsd.rs
@@ -8,15 +8,15 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use target::Target;
+use target::{Target, TargetResult};
 
-pub fn target() -> Target {
+pub fn target() -> TargetResult {
     let mut base = super::freebsd_base::opts();
     base.cpu = "x86-64".to_string();
     base.max_atomic_width = 64;
     base.pre_link_args.push("-m64".to_string());
 
-    Target {
+    Ok(Target {
         llvm_target: "x86_64-unknown-freebsd".to_string(),
         target_endian: "little".to_string(),
         target_pointer_width: "64".to_string(),
@@ -26,5 +26,5 @@ pub fn target() -> Target {
         target_env: "".to_string(),
         target_vendor: "unknown".to_string(),
         options: base,
-    }
+    })
 }
diff --git a/src/librustc_back/target/x86_64_unknown_linux_gnu.rs b/src/librustc_back/target/x86_64_unknown_linux_gnu.rs
index 7908e0d581ba1..ef81d397a8f1e 100644
--- a/src/librustc_back/target/x86_64_unknown_linux_gnu.rs
+++ b/src/librustc_back/target/x86_64_unknown_linux_gnu.rs
@@ -8,15 +8,15 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use target::Target;
+use target::{Target, TargetResult};
 
-pub fn target() -> Target {
+pub fn target() -> TargetResult {
     let mut base = super::linux_base::opts();
     base.cpu = "x86-64".to_string();
     base.max_atomic_width = 64;
     base.pre_link_args.push("-m64".to_string());
 
-    Target {
+    Ok(Target {
         llvm_target: "x86_64-unknown-linux-gnu".to_string(),
         target_endian: "little".to_string(),
         target_pointer_width: "64".to_string(),
@@ -26,5 +26,5 @@ pub fn target() -> Target {
         target_env: "gnu".to_string(),
         target_vendor: "unknown".to_string(),
         options: base,
-    }
+    })
 }
diff --git a/src/librustc_back/target/x86_64_unknown_linux_musl.rs b/src/librustc_back/target/x86_64_unknown_linux_musl.rs
index 3301e0e0dc93f..4bad7754b3907 100644
--- a/src/librustc_back/target/x86_64_unknown_linux_musl.rs
+++ b/src/librustc_back/target/x86_64_unknown_linux_musl.rs
@@ -8,15 +8,15 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use target::Target;
+use target::{Target, TargetResult};
 
-pub fn target() -> Target {
+pub fn target() -> TargetResult {
     let mut base = super::linux_musl_base::opts();
     base.cpu = "x86-64".to_string();
     base.max_atomic_width = 64;
     base.pre_link_args.push("-m64".to_string());
 
-    Target {
+    Ok(Target {
         llvm_target: "x86_64-unknown-linux-musl".to_string(),
         target_endian: "little".to_string(),
         target_pointer_width: "64".to_string(),
@@ -26,5 +26,5 @@ pub fn target() -> Target {
         target_env: "musl".to_string(),
         target_vendor: "unknown".to_string(),
         options: base,
-    }
+    })
 }
diff --git a/src/librustc_back/target/x86_64_unknown_netbsd.rs b/src/librustc_back/target/x86_64_unknown_netbsd.rs
index 7e6d1b78469e2..5145e52d6b4c9 100644
--- a/src/librustc_back/target/x86_64_unknown_netbsd.rs
+++ b/src/librustc_back/target/x86_64_unknown_netbsd.rs
@@ -8,14 +8,14 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use target::Target;
+use target::{Target, TargetResult};
 
-pub fn target() -> Target {
+pub fn target() -> TargetResult {
     let mut base = super::netbsd_base::opts();
     base.max_atomic_width = 64;
     base.pre_link_args.push("-m64".to_string());
 
-    Target {
+    Ok(Target {
         llvm_target: "x86_64-unknown-netbsd".to_string(),
         target_endian: "little".to_string(),
         target_pointer_width: "64".to_string(),
@@ -25,5 +25,5 @@ pub fn target() -> Target {
         target_env: "".to_string(),
         target_vendor: "unknown".to_string(),
         options: base,
-    }
+    })
 }
diff --git a/src/librustc_back/target/x86_64_unknown_openbsd.rs b/src/librustc_back/target/x86_64_unknown_openbsd.rs
index 823b0994b0a00..339dbd591a02e 100644
--- a/src/librustc_back/target/x86_64_unknown_openbsd.rs
+++ b/src/librustc_back/target/x86_64_unknown_openbsd.rs
@@ -8,15 +8,15 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use target::Target;
+use target::{Target, TargetResult};
 
-pub fn target() -> Target {
+pub fn target() -> TargetResult {
     let mut base = super::openbsd_base::opts();
     base.cpu = "x86-64".to_string();
     base.max_atomic_width = 64;
     base.pre_link_args.push("-m64".to_string());
 
-    Target {
+    Ok(Target {
         llvm_target: "x86_64-unknown-openbsd".to_string(),
         target_endian: "little".to_string(),
         target_pointer_width: "64".to_string(),
@@ -26,5 +26,5 @@ pub fn target() -> Target {
         target_env: "".to_string(),
         target_vendor: "unknown".to_string(),
         options: base,
-    }
+    })
 }
diff --git a/src/librustc_driver/lib.rs b/src/librustc_driver/lib.rs
index 0a8df923b846b..eff920608dc2a 100644
--- a/src/librustc_driver/lib.rs
+++ b/src/librustc_driver/lib.rs
@@ -609,7 +609,7 @@ impl RustcDefaultCalls {
         for req in &sess.opts.prints {
             match *req {
                 PrintRequest::TargetList => {
-                    let mut targets = rustc_back::target::TARGETS.to_vec();
+                    let mut targets = rustc_back::target::get_targets().collect::<Vec<String>>();
                     targets.sort();
                     println!("{}", targets.join("\n"));
                 },